This invention relates to machine tools in general and, in particular, to a milling machine for use with cylindrical work. More particularly the invention deals with a milling machine of the type having a rotary annular tool with internal cutting edges for machining the crankshafts of multicylinder internal combustion engines, among other objects.
A variety of devices have been suggested and used for machining the crankpins, as well as journals, of crankshafts. Typical of such prior art machines are those suggested by U.S. Pat. Nos. 3,880,025 and 4,276,749. The former proposes the use of a compound slide mechanism, with the slides laid at right angles with each other, for the desired planetary motion of the cutting tool. As the slides are required to travel parallel to each other, however, the compound slide mechanism requires complex means to that end. An additional drawback is the great distance between the front of the machine and the aligned axis of the work holding chucks, making the operability of the machine poor.
The second mentioned U.S. patent employs two eccentric rings to provide varying degrees of eccentricity required for machining different crankpins. However, the maximum degree of eccentricity offered by this known mechanism is inconveniently small in relation to the size of the complete machine, a further increase in the degree of eccentricity being possible only by making the machine too bulky.